1. Field of the Invention
The present invention relates to apparatus for cooling a microelectronic die. In particular, the present invention relates to a heat dissipation device including an active noise canceling mechanism.
2. State of the Art
Higher performance, lower cost, increased miniaturization of integrated circuit components, and greater packaging density of integrated circuits are ongoing goals of the microelectronics industry. As these goals are achieved, microelectronic dice become smaller. Accordingly, the density of power consumption of the integrated circuit components in the microelectronic die has increased, which, in turn, increases the average junction temperature of the microelectronic die. If the temperature of the microelectronic die or particular areas on the microelectronic die becomes too high, the integrated circuits of the microelectronic die may be damaged (which can result in system reliability problems) or destroyed (system failure).
Such damage or destruction is avoided by thermally attaching heat dissipation devices to the microelectronic die. FIG. 4 illustrates an exemplary heat dissipation device (shown as a finned heat slug 202) attached to a microelectronic die 204 with a layer of thermally conductive adhesive 212. The microelectronic die 204 is electrically attached to a carrier substrate 206 through a plurality of electrical interconnects (shown as first solder balls 208). A fan assembly 214 is usually attached to the finned heat slug 202 which enhances convective heat dissipation by forcing ambient air through the finned heat slug 202.
Another known method of removing heat from a microelectronic die is the use of a heat pipe 220, as shown in FIG. 5. A heat pipe 220 is a simple device that can quickly transfer heat from one point to another without the use of electrical or mechanical energy input. The heat pipe 220 is generally formed by evacuating air from a sealed pipe 222 which contains a xe2x80x9cworking fluidxe2x80x9d 224, such as water or alcohol. The sealed pipe 222 is oriented with a first end 226 proximate a heat source 228. The working fluid 224, which is in a liquid phase proximate the heat source 228, increases in temperature and evaporates to form a gaseous phase of the working fluid 224, which moves (shown by arrows 232) toward a second end 234 of the sealed pipe 222. As the gaseous phase moves toward the sealed pipe second end 234, it condenses to again form the liquid phase of the working fluid 224, thereby releasing the heat absorbed during the evaporation of the liquid phase of the working fluid 224. The liquid phase returns, usually by capillary action or gravity, to the sealed pipe first end 226 proximate the heat source 228, wherein the process is repeated. Thus, the heat pipe 220 is able to rapidly transfer heat away from the heat source 228. Various configurations of heat pipes have been used to cool microelectronic dice and they have been used in conjunction with finned heat slugs 202 and fan assemblies 214 (FIG. 4).
Although these heat dissipation methods are adequate to cool most microelectronic dice, they cannot fully address the heat dissipation requirements of high temperature generating microelectronic dice. One method of addressing the heat dissipation requirements is the use of a refrigeration-type cooling method, as known in the art. However, such refrigeration-type methods are prohibitively expensive. Another method of addressing such heat removal is to simply increase the size or speed (rpm) of the fans (see fan assembly 214 of FIG. 4). However, this increases the noise generated by the fan. Unfortunately, personal computer (xe2x80x9cPCxe2x80x9d) manufactures have set fan noise limits to about 24 decibels (avg.) at 1 meter from a PC case and about 29 decibels (avg.) at 1 meter from a liquid crystal display desktop PC case. Thus, only increasing the size or speed of the fans is not an adequate solution.
Therefore, it would be advantageous to develop a heat dissipation device and techniques to cost effectively control heat removal from a microelectronic die, while not increasing the noise generated by the heat dissipation device.